1. Field of the Invention
The present invention relates to a valve assembly and more particularly to a such a valve assembly which is operable dependably and efficiently to control the flow of fluids through a fluid system initiating and terminating the flow of fluid in response to a predetermined command with little or no pressure loss when in an opened condition and without the leakage associated with prior art valve assemblies when in a closed condition.
2. Description of the Prior Art
Fluid control valves form an essential part of virtually all fluid systems. A broad operational objective of such valves is to form an absolute seal preventing flow along a fluid line until, in accordance with a predetermined command, it is desired to permit fluid to pass along the line. When the initiation of such fluid flow is desired, the broad operational objective is instantaneously to open to permit the flow of fluid along the line for the preselected period of time and thereafter instantaneously to close instantaneously terminating the flow of fluid along a line. Upon such closure, it is desired that there be no leakage of fluid along the line due to fluid passing through the valve.
While these broad operational objectives are both simple and universal, full achievement of the objectives has not heretofore been obtained.
Conventional valves have heretofore been of three main types. A conventional gate valve is typically manually operated and is composed simply of a conduit having a gate member which is moved along a path at right angles to the longitudinal axis of the conduit reaching a closed position in which it is intended that the gate member fully occlude the fluid passage. Such gate valves have the operational advantage of causing little or no loss of fluid pressure when in a fully opened condition since, except for turbulence, the fluid passage therethrough is essentially entirely unobstructed. However, such valves are chronically subject to fluid leakage through the gate member when otherwise in a closed condition. Furthermore, their operation does not lend itself to satisfactory performance when operated other than manually.
A second general type of conventional valve is a conventional diaphragm valve. Such valves are characterized by a wall disposed in the fluid passage at the site of the valve to divert the fluid flow along a course at right angles to the normal fluid passage and against a diaphragm. The diaphragm, when in a normally closed attitude, is intended sealing to engage the upper edge of the wall to prevent the fluid from passing about the wall and back along its course. The diaphragm is typically retained in a closed condition by bleeding fluid from the upstream side of the valve to pressurize the chamber above the diaphragm overriding normal fluid pressure in a passage and retaining the valve in a closed condition. When it is desired to open the valve, the fluid pressure in the chamber above the diaphragm is relieved therefrom so that the pressure within the normal fluid passage becomes greater than that above the diaphragm thereby causing the diaphragm to involute moving away from the upper edge of the wall and permitting fluid to flow in the passage over the top of the wall and back along the normal fluid stream. Such conventional diaphragm valves are compatible with automatic operation systems, but also suffer from fluid leakage when in the closed condition. More disturbingly, such valves create a rather substantial pressure loss when in a fully opened condition due to the wall obstructing the fluid passage and the inherent constriction of the fluid passage through the valve.
Still another type of conventional valve is a spherical diaphragm valve in which the fluid passage through the valve is substantially unobstructed except for a rather low wall opposite the diaphragm and engaged by and cooperatively operable with a larger diaphragm substantially in the manner heretofore described to control the flow of fluid along the fluid passage. Such spherical diaphragm valves are advantageous when compared to conventional diaphragm valves in that a comparatively small pressure loss is caused when the valve is in an opened condition because of the relatively low profile wall as compared with a conventional diaphragm valve. Conversely, such spherical diaphragm valves are chronically subject to fluid leakage because the diaphragm is largely unsupported when in a closed condition. Thus, while counterbalancing fluid pressure above the diaphragm is substantial, the fluid pressure within the main fluid passage bears against the diaphragm and tends to displace it from the low wall so as to cause leakage thereby. Thus, it will be seen that all conventional valves fail to meet the optimum operational objectives of fluid valves.
Therefore, it has long been known that it would be desirable to have a valve assembly which substantially achieves the optimum operational objectives of a fluid valve in that when in a normally closed condition the valve forms a fluid tight seal against fluid passing therebeyond along the fluid line permitting no leakage; which is instantaneously responsive to a predesignated command to open to a fully opened condition such that little or no pressure loss is caused; and which, upon receipt of the predesignated command, operates instantaneously again to close substantially completely to seal the fluid line through the valve with substantially no fluid leakage.